Researchers at the National Institute of Standards and Technology (NIST) have demonstrated a new imaging system that detects naturally occurring terahertz radiation with unprecedented sensitivity and resolution. The technology may become a new tool chemical and biochemical analyses ranging from early tumor detection to rapid and precise identification of chemical hazards for homeland security instruments.
Terahertz radiation falls between microwaves and infrared radiation on the electromagnetic spectrum, with frequencies from about 300 million cycles per second to about 3 trillion cycles per second. Biological and chemical samples naturally emit characteristic signatures of terahertz radiation, but detecting and measuring them is a unique challenge because the signals are weak and absorbed rapidly by the atmosphere. The NIST prototype imager, described in detail for the first time in a new paper,* uses an exquisitely sensitive superconducting detector combined with microelectronics and optics technologies to operate in the terahertz range. The NIST system has its best resolution centered around a frequency of 850 gigahertz, a transmission window where terahertz signals can pass through the atmosphere. The system can detect temperature differences smaller than half a degree Celsius, which helps to differentiate between, for example, tumors and healthy tissue.
The heart of the system is a tiny device that measures incoming terahertz radiation by mixing it with a stable internal terahertz signal. This mixing occurs in a thin-film superconductor, which changes temperature upon the arrival of even a minute amount of radiation energy. The slight frequency difference between the two original terahertz signals produces a more easily detected microwave frequency signal.
NIST developed the device and antenna, combined with an amplifier on a chip smaller than a penny, in collaboration with the University of Massachusetts. Called
|Contact: Laura Ost|
National Institute of Standards and Technology (NIST)